Update_Password Action Theme

Hello community,

I am currently trying to theme our company keycloak and I am stumbling across an issue I cannot solve yet:

I am updating the email theme so it sends an email fitting my companys needs. This email is being sent when UPDATE_PASSWORD is invoked. This generates a link for the user to update his password. The problem here is, that the page that is shown is not correctly themed and is using the default theme layout/stylesheet and not the one I created.
As far as I understand, this is not something I can achieve in the email theme but in the login theme. I checked the default base theme and found a file like:
login-update-password.ftl

As far as I understand, this template is the one being used when I invoke UPDATE_PASSWORD on the users credentials. So I copied this file to my login theme but it has no effect. At the top, this template imports the template.ftl as layout. My login theme also has the template.ftl which I already modified and which also works. However, the page that opens after clicking the email link does always use the default template als layout.
When users click on “forgot password” on the login page, the layout will always be themed correctly. It’s just the link in the email that does not do any magic for me.
What am I missing here? Thanks in advance!